Warning: Videos that appear in this article may include graphic content

Despite rumors, Las Vegas authorities still believe only man was responsible for killing at least 59 people and injuring 527 after he opened fire on an outdoor concert late Sunday. It is now the deadliest mass shooting in modern U.S. history.

Around 10 p.m. local time, a gunman opened fire on the Route 91 Harvest Festival from inside the Mandalay Bay Resort and Casino across the street.

SWAT teams quickly surrounded the concert and the casino, and officers used explosives to get into the hotel room where the suspect was inside, authorities said. The gunman, identified as 64-year-old Stephen Paddock, was found dead. Police believe he killed himself prior to their entry.

Overall 23 guns, including a number of long rifles, were found in his room, Las Vegas Police Undersheriff Kevin McMahill told CNN.

Eric Paddock

Suspected Las Vegas gunman Stephen Paddock

Paddock is from Mesquite, Nev., about 80 miles northeast of Las Vegas. Clark County Sheriff Joseph Lombardo says Paddock first checked into the hotel on Sept. 28.

Authorities obtained a search warrant for the home of Stephen Paddock in Mesquite, Nevada.

Authorities stormed the house, which is in an upscale neighborhood, on Monday afternoon. They closed a two-block stretch around the house in a neighborhood that has a community clubhouse with a tennis court and a billiard room.

Police say they located 62-year-old Marilou Danley, who was initially wanted as a person of interest in this incident. Danley, who was out of the country at the time, is not believed to have been involved in the shooting.

There was no immediate word on the motive for the bloodbath. Lombardo said authorities believe it was a “lone wolf” attack.

Without providing evidence, the Islamic State claimed the attack, saying the shooter converted to Islam months ago. FBI officials later disputed this report, saying that there is no known link between the suspect and any international terror group.

Mesquite police also searched the suspected gunman's home. At a press conference, authorities say they seized in excess of 18 additional firearms, in additional to some explosives and several thousand rounds of ammo. Another residence in Northern Nevada is about to be searched by SWAT teams, police said.

Eric Paddock, who lives in Florida, told the Orlando Sentinel: “We are completely dumbfounded. We can’t understand what happened.”

Eric Paddock told WESH that "it's like an asteroid has hit the family," and that the family has "no reason, rhyme, rationale" for the attack. They say he had no criminal past and no group affiliation. The Paddock family says the alleged shooter was a multi-millionaire real estate investor.

Eric shared an image of himself with Stephen, pictured below, from 15 years ago.

Eric Paddock

Two Las Vegas police officers are being treated at a local hospital for injuries they sustained during the shooting, Lombardo said. In addition, the sheriff stated that there were off duty officers attending the concert who died, including a LVMPD officer.

Country music star Jason Aldean was performing at the end of the three-day festival when the gunman opened fire.

Video of the shooting then showed Aldean stopping and the crowd getting quiet as if they were unsure of what had just happened. The gunman paused and then fired another volley of muzzle flashes from the gold glass casino as more victims fell to the ground while others fled in panic.

As the 22,000 fans in the crowd began to flee, witnesses reported seeing flashes of light coming from the Mandalay Bay tower high above.

A witness, only identified as Christine, describes the horrifying moment:

"We saw Jason run off stage, and people all over on the floor the grassy area in front of the stage, someone falling, someone screaming and running," she said. "The shots just kept coming, and so we were going down and when we got down, there was a man that was shot right there, he was all bloody and unconscious."

Monique Dumas said that everyone instantly crouched when they heard the shots.

"It seemed there was a pause in the gunfire and the people in the yellow shirts were telling the people to 'go, go, go, go' ... the gunfire never ended, it seemed like it went on and on and on," she said.

A nurse who was off-duty witnessed the scene described it.

Storme Warren described watching the chaos erupt once people began to run for their lives, saying: "We stepped over the bodies, we saw the people, we saw the heart-wrenching sadness from relatives grabbing hold of their loved ones."

Flights in and out of Las Vegas' McCarran Airport were also held because of the situation.

Aldean took to social media to say he and his crew are safe, adding: "Tonight has been beyond horrific."

Lt. Gov. Mark Hutchinson told reports that all victims who had been transported to University Medical Center of Southern Nevada survived the injuries sustained in the shooting. "If you were alive and went into UMC hospital last night, you are still alive," said Hutchison.

UMC is the only Level I trauma center in the state of Nevada.

MGM Resorts, the owners of the Mandalay Bay Casino, tweeted: "Our thoughts & prayers are with the victims of last night's tragic events. We’re grateful for the immediate actions of our first responders."

"We need to come together and fight for America, because this is our country, this is our nation, this is our people, we need to stand together to fight this thing out," he said.

49 people were killed when a gunman opened fire at the Pulse nightclub in Orlando in June 2016.

Orlando Police Chief John Mina tweeted condolences for all those affected by the mass shooting in Las Vegas, saying in part: "This community, and the men and women of OPD, know all too well the anguish that is gripping the residents, visitors and law enforcement community in Las Vegas."